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Pigmented Skin Lesions

MELANOMA

MELANOMA

Malignant melanoma is a skin cancer due to uncontrolled growth of pigment cells -melanocytes.

Melanocytes

• Normal melanocytes occur in the basal layer of the epidermis

• They produce melanin• Melanin (a protein) protects the skin by absorbing

ultraviolet (UV) radiation • Melanocytes are found in equal numbers in black and in

white skin• Melanocytes in black skin produce much more melanin• Non-cancerous growth of melanocytes results in moles

(benign melanocytic naevi) and freckles• Cancerous growth of melanocytes results in melanoma

Risk Factors for Melanoma

• Sun exposure, particularly during childhood • Fair skin that burns easily • Blistering sunburn, especially when young • Previous melanoma • Previous non-melanoma skin cancer (BCC,

SCC) • Family history of melanoma• Large numbers of moles (esp if > 100) • Abnormal moles (atypical or dysplastic naevi)

Epidemiology of Melanoma

• 3% of all cancers and 10% of skin cancers.• Incidence 1:10,000 per annum • Incidence is increasing in developed countries • Incidence rises with age, rare in children,

commonest in over 75s • 3rd commonest cancer in young people. • In UK 2002 - 1,640 deaths from malignant melanoma

Over 65% of deaths from malignant melanoma were in the over 65s.

• It is commoner in women than in men but men have a worse prognosis.

Melanoma in situ

• Superficial forms of melanoma spread out within the epidermis (horizontal growth).

• If all the melanoma cells are confined to the epidermis, it is melanoma in situ.

• Lentigo maligna is a special case of melanoma in situ that occurs around hair follicles on the sun damaged skin of the face or neck.

• Melanoma in situ is cured by excision

Invasive Melanoma

• When the cancerous cells have grown through the basement membrane into the deeper layer of the skin (the dermis), it is known as invasive melanoma (vertical growth)

• Nodular melanoma appears to be invasive from the beginning, and has little or no relationship to sun exposure.

• Metastatic disease increases in likelihood with increasing depth of the melanoma.

• 15% of people with invasive melanoma will die from it.

Where do melanomas occur?• Melanoma can arise from otherwise normal appearing skin (50%) • Or from within a mole or freckle, which starts to grow larger and

change in appearance. Precursor lesions include: – Congenital melanocytic naevus (brown birthmark) – Atypical or dysplastic naevus (funny-looking mole) – Benign melanocytic naevus (normal mole)

• Melanomas occur anywhere on the skin, not only in sun-exposed areas. Commonest sites: men - back (40%), women - leg (40%).

• Melanomas can also occur on mucous membranes (lips, genitals). • May also occurs in other parts of the body such as the eye, brain,

mouth or vagina.

Moles (Melanocytic Naevi)

• Very common

• May be flat or protruding

• Vary in colour from pink to black

• Brown or black coloured moles are also called ‘pigmented naevi’.

• Mostly round or oval in shape

• Range in size from 2mm to several cm

Moles

• Most frequently moles arise during childhood or early adult life (acquired melanocytic naevi).

• Exposure to sunlight increases the number of moles.

• Teenagers and young adults tend to have the greatest number of moles.

Classification

• Junctional naeviGroups or nests of naevus cells at the junction of the epidermis and dermis. Tend to be flat colourful moles.

• Dermal/Intradermal naeviNests of naevus cells in the dermis. These moles are thickened and often protrude from the skin surface (papillomatous naevi).

• Compound naeviNests of naevus cells at the epidermal-dermal junction as well as within the dermis. These moles have a central raised area surrounded by flat pigmentation.

Junctional Naevus

Congenital Melanocytic Naevus

• Brown or black naevi • Present at birth or develop in the first year or so

of life • Moles that look like birthmarks but were not

present at birth may be called ‘congenital naevus-like’ naevi or ‘congenital-type’ naevi.

• About one baby in 100 has a small or medium sized congenital naevus, so they are quite common.

• Very large, giant or bathing trunk naevi are very rare.

Types of congenital melanocytic naevus

• Typically multi-shaded, oval, fairly uniform pigmented patches• Most grow with the child but become proportionally smaller and less

obvious with time. • May darken, become bumpy or hairy especially at puberty. • Rarely fade away or disappear. • Congenital melanocytic naevi in adults are classed as ‘small’ (<

1.5cm di), ‘medium’ (>1.5 <10cm) or ‘large’ (>10cm) • ‘Giant’ congenital naevi are greater than 20cm in diameter. Often

found on the buttocks (‘bathing trunk’ naevi) • Café-au-lait macule - a flat tan mark, usually oval (inherited).

Multiple café-au-lait macules may be a sign of neurofibromatosis. • Speckled lentiginous naevus (naevus spilus) has dark spots

scattered on a flat tan background.

Risk of Melanoma

• The risk of melanoma in a small or medium-sized congenital melanocytic naevus is very small (< 1%)

• Melanoma never arises from café-au-lait macules

• Melanoma is more likely in the giant naevi (~ 5% over a lifetime) especially in those that lie across the spine

Congenital Melanocytic Naevus

Café au lait Macule

Giant Melanocytic Naevus

Speckled Melanocytic Naevus

Atypical Naevi

• Melanocytic naevi with unusual features eg indistinct edge, larger size.

• May resemble Malignant Melanomoa but are benign• Sometimes called dysplastic naevi, active junctional

naevi, B-K moles and Clark's naevi. • May be familial or sporadic. • The inherited form is usually part of a syndrome -

Familial Atypical Mole and Melanoma (FAMM) syndrome (formerly dysplastic naevus syndrome). – One or more first-degree or second-degree relative with

malignant melanoma – A large number of naevi (often more than 50) some of which are

atypical naevi – Naevi that show certain histological features.

Atypical Naevi

Fair-skinned individuals with light coloured hair and freckles are most at risk of getting atypical naevi, especially if they have been frequently exposed to the sun or have a family history of atypical naevi.

Atypical naevi may develop at any time but most develop during the first 15 years of life.

Atypical Naevi

• People with one to four atypical naevi have a slightly higher risk than the general population of developing malignant melanoma

• People with FAMM syndrome are significantly more at risk of developing melanoma.

• Atypical naevi are harmless (benign) and do not need to be removed. However, it is not always easy to tell whether a lesion is an atypical naevus or a melanoma, so if in doubt, it should be removed by excision biopsy.

Atypical Naevus

Atypical Naevus

Glasgow 7-point Checklist

• Major features– Change in size – Irregular shape – Irregular colour

• Minor features – Diameter >7mm – Inflammation – Oozing – Change in sensation

ABCDE of Melanoma

A. Asymmetry

B. Border - irregularity

C. Colour - variation

D. Diameter - over 6 mm

E. Evolving - (enlarging, changing)

Types of Melanoma

• Flat patches (horizontal slow growth) – Superficial spreading melanoma (SSM) – Lentigo maligna melanoma (sun damaged skin of face, scalp

and neck) – Acral lentiginous melanoma (on soles of feet, palms of hands or

under the nails – the subungual melanoma)

• Nodules (vertical rapid growth)– Nodular melanoma – Mucosal melanoma (arising on lips, eyelids, vulva, penis, anus) – Desmoplastic melanoma (fibrous tumour with a tendency to

grow down nerves)

• Combinations occur e.g. nodular melanoma arising within a superficial spreading melanoma.

Typical Superficial Spreading Melanoma

Superficial Spreading Melanoma with regression

Amelanotic Melanoma

Lentigo Maligna

Lentigo Maligna Melanoma

Lentigo Maligna

• Sun-exposed areas of the face and neck• Elderly• Slow growing • Often quite large (>20mm). • Pre-cancerous • Conversion to a lentigo maligna melanoma

occurs in ~ 5% of patients • Identifying lesions that require referral is not

easy – but see ABCDE

Nodular Melanoma in Lentigo Maligna

Acral Lentiginous Melanoma

Subungual Melanoma

Amelanotic Subungual Melanoma

Nodular Melanoma

Nodular Melanoma

Nodular Melanoma

Diagnosis

• Excision biopsy with a 2 to 3-mm margin• Breslow depth - thickness of the

melanoma in mm • Clark's level - describe which layer of the

skin has been breached. Clark’s level 1 refers to melanoma in situ. Invasive melanoma may reach Clark's level 2 (thin) to 5 (reaching the subcutaneous fat layer).

• Systematic search for metastasis

Prognosis

Death is unlikely if a melanoma has a Breslow thickness of less than 1mm

50% dead within 5 years if >4mm